A central issue in the case is Rule 15(c)(1)(C)'s requirement of a "mistake concerning the proper party's identity." On what qualifies as a "mistake," the argument includes this priceless exchange involving Justice Breyer and Justice Scalia:

JUSTICE BREYER: Have you ever driven a car where your wife has said turn left and you have turned right?

(Laughter.)

JUSTICE BREYER: Has that ever happened to you?

MR. GLAZIER: Yes.

. . .

JUSTICE BREYER: . . . Did you do it by mistake? Yes, of course, you did. It's happened to every human being. There are millions of instances in which people do things by mistake where, in fact -

JUSTICE SCALIA: I think your wife made a mistake. I don't think you made a mistake.